A variety of vacuum-electric control units or devices have been employed for controlling automotive heating, ventilating and air conditioning systems. Control units of one type have employed a single movable function control member, such as a lever or slider, having a multiplicity of positions, corresponding with the desired functional modes of operation. The multiposition lever or slider may operate one or more multiposition vacuum control valves and one or more electrical switches. The switches may control the energization of a blower motor and an air conditioning clutch, whereby an air conditioning compressor is driven by the engine of the vehicle. The multiposition vacuum control valve may supply intake manifold vacuum to various vacuum motors for operating doors or valve plates in the air duct system, for controlling the movement of air to and from the desired locations in the system.
In addition to the function control member, there is often a heat control member, which may be in the form of a movable lever or slider, for regulating the amount of heat supplied by the system, and a multiposition blower speed control switch, for regulating the speed of the blower motor.
There are also control units of the push button type, having a series of push buttons for selecting the various operating functions or modes. In a prior construction of one type, the push buttons operate a complex mechanical selector mechanism, whereby each push button actuates selected control elements, which may include a selected vacuum control valve or a selected electrical switch, or both. The selector mechanism may utilize cam action selectors or linkage plate selectors. Such push button control units tend to be rather complex in construction.
Another type of prior construction has employed a plurality of push buttons, each of which operates a separate vacuum valve to accomplish a particular control function. Thus, for example, there may be four push buttons and four vacuum valves, each of which may be operated by one of the push buttons. The push buttons may latch down individually. In some cases, more than one push button may be operated simultaneously.
There has also been another type of prior construction which has employed a plurality of push buttons, each of which operates a separate electrical switch to accomplish a particular electrical control function. The push buttons may latch down individually.